In the opening minutes of trading on the Nasdaq the stock rose 10 percent to $11.00. But then they fall back and were down 1 percent at $9.90.

When asked about the price drop, CEO Mark Pincus said in an interview there were "no regrets."

"Our approach has always been to focus on the longterm," Pincus said. "We thought this was the right time to go public."

"We're going to focus on the products and business results we deliver in the next four to eight quarters and hope the stock market values and appreciates that as they see us deliver it," he added.

The company, which competes with Electronic Arts, sold 100 million shares of Class A common stock at $10 per share in the IPO, roughly 11 percent of its shares on a diluted basis, at the top end of the $8.50 to $10 indicative range.

Zynga wants to avoid what happened to Groupon Inc, another closely watched Internet IPO that rose on its first day of trading in November but slumped below its $20 issue price about three weeks later

Zynga's IPO had been highly anticipated because it is seen as a way for investors to get a slice of Facebook's growth before the social network itself goes public. About 95 percent of its revenue comes from Facebook, where it makes money from selling virtual items such as virtual jewelry and poker chips in its games.

Unlike Groupon, Zynga is profitable, but less than 3 percent of its players spend money on items in its free games.

At $1 billion in proceeds, Zynga's IPO would still be the largest from a U.S. Internet company since Google Inc raised $1.9 billion in 2004.

(Reporting By Liana B. Baker)

• A Permanent Economic Emergency